Four wave mixing (FWM) in optical communication systems employing multiple carrier wavelengths may lead to beat products at optical frequencies f1±f2, f1±f3 and f1±2f2, where f1, f2, f3 are the optical frequencies of carriers in the wavelength plan that participate in creating these beat products. For more than three carriers any combination of 3 and 2 carriers participates in generating these beat products. When the beat products end up at the same optical frequency of any of the other optical frequencies in the channel plan, mixing of the carrier and beat product takes place such that unwanted noise and distortions are generated. Thus it is desirable to prevent the beat products from superimposing with the carriers.
Optical communication systems may also suffer from distortions and noise due to Stimulated Raman Scattering (SRS) and other fiber effects. Component heating and degradation over time may cause wavelength drift and other undesirable effects. It is desirable to reduce the effects of SRS and other distortions and noise while maintaining dense wavelength spacing and, if possible, backward compatibility with existing optical communication components.